Metal pipes for oil wells

Abstract

Provided is a metal pipe for an oil well, the metal pipe comprising a Zn-Ni alloy plated layer having high adhesiveness. A metal pipe for an oil well according to the present disclosure comprises: a pipe body which includes a pin formed on a first end part and including a pin contact surface having a male screw part, and a box formed on a second end part and including a box contact surface having a female screw part; and a Zn-Ni alloy plated layer formed on at least one among the pin contact surface and the box contact surface. The X-ray diffraction intensity of the Zn-Ni alloy plated layer satisfies expression (1).　I18 / (I18+I36+I54)≥0.60 (1) Here, the X-ray diffraction intensity of 411 and 330, the X-ray diffraction intensity of 442 and 600, and the X-ray diffraction intensity of 552 are substituted, in a unit of cps, for I18, I36, and I54 in expression (1), respectively.

Description

[Technical field]

[0001] The present disclosure relates to a metal pipe for oil wells, and more particularly to a metal pipe for oil wells having a threaded joint formed therein. [Background technology]

[0002] Metal oil well pipes are used for the mining of oil fields and natural gas fields (hereinafter, oil fields and natural gas fields are collectively referred to as "oil wells"). Specifically, in an oil well mining site, a plurality of metal oil well pipes are connected according to the depth of the oil well to form an oil well pipe connection body, typically casing or tubing. An oil well pipe connection body is formed by screwing together threaded joints formed at the ends of metal oil well pipes. Inspection may be performed on the oil well pipe connection body. When inspection is performed, the oil well pipe connection body is pulled up and the threaded joints are unscrewed. Then, the oil well pipe connection body that has been unscrewed and removed from the oil well pipe connection body is inspected. After inspection, the threaded joints of the metal oil well pipes are screwed again and reused as part of the oil well pipe connection body.

[0003] The metal oil well pipe comprises a pipe body having a first end and a second end. The pipe body includes a pin formed at the first end and a box formed at the second end. The pin has a pin contact surface including a male thread portion on an outer circumferential surface of the first end of the pipe body. The box has a box contact surface including a female thread portion on an inner circumferential surface of an end (second end) of the pipe body opposite the pin. When a threaded joint formed at an end of the metal oil well pipe is screwed, the pin contact surface comes into contact with the box contact surface.

[0004] The pin contact surface and the box contact surface are repeatedly subjected to strong friction when the metal pipe for oil well use is screwed in and out. If these parts do not have sufficient durability against friction, galling (irreparable seizure) will occur when the pipe is repeatedly screwed in and out. Therefore, metal pipe for oil well use is required to have sufficient durability against friction, i.e., excellent seizure resistance.

[0005] Conventionally, compound grease containing heavy metals, called dope, has been used to improve seizure resistance. The seizure resistance of oil well metal pipes can be improved by applying compound grease to the pin contact surface and / or box contact surface. However, heavy metals such as Pb, Zn, and Cu contained in compound grease may have an adverse effect on the environment. For this reason, there is a demand for the development of oil well metal pipes that have excellent seizure resistance without using compound grease.

[0006] In the metal pipe for oil wells disclosed in Patent Document 1 (WO 2016 / 170031), a Zn-Ni alloy plating layer is formed on the pin contact surface or the box contact surface instead of compound grease. Zn in the Zn-Ni alloy plating layer formed on the contact surface of the metal pipe for oil wells enhances the corrosion resistance of the metal pipe for oil wells by sacrificial corrosion protection. Furthermore, Patent Document 1 discloses that the Zn-Ni alloy also has excellent wear resistance. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2016 / 170031 Summary of the Invention [Problem to be solved by the invention]

[0008] Incidentally, when the metal pipe for oil wells is screwed and unscrewed, the Zn-Ni alloy plating layer is also repeatedly subjected to strong friction. If a part of the Zn-Ni alloy plating layer is peeled off due to repeated strong friction, the friction coefficient of the contact surface increases rapidly, and the seizure resistance of the metal pipe for oil wells is rapidly reduced. Therefore, it is preferable that the Zn-Ni alloy plating layer formed on the contact surface of the metal pipe for oil wells is not easily peeled off even when repeatedly subjected to strong friction. Hereinafter, in this specification, being not easily peeled off even when repeatedly subjected to strong friction is also referred to as having "high adhesion."

[0009] According to the technology disclosed in the above Patent Document 1, the galling resistance of the metal pipe for oil well use can be improved by forming a Zn-Ni alloy plating layer on the contact surface of the pin or the contact surface of the box. However, the above Patent Document 1 does not discuss the adhesion of the Zn-Ni alloy plating layer formed on the contact surface of the metal pipe for oil well use.

[0010] An object of the present disclosure is to provide a metal oil well pipe having a Zn-Ni alloy plating layer with high adhesion. [Means for solving the problem]

[0011] The metal pipe for oil well use according to the present disclosure comprises: a tube body including a first end and a second end; The tube body includes: A pin formed on the first end; a box formed at the second end; The pin is a pin contact surface including an external thread; The box includes: a box contact surface including an internal thread; The oil well metal pipe further comprises: a Zn-Ni alloy plating layer formed on at least one of the pin contact surface and the box contact surface; The X-ray diffraction intensity of the Zn—Ni alloy plating layer satisfies formula (1). I 18 / (I 18 +I 36 +I 54 )≧0.60 (1) Here, I in formula (1) 18 The X-ray diffraction intensities of {411} and {330}, where the sum of the squares of the Miller indices is 18, are substituted in the unit of cps. 36 The X-ray diffraction intensities of {442} and {600}, which have a sum of squares of Miller indices of 36, are substituted in the unit of cps for I 54 is substituted with the X-ray diffraction intensity of {552}, where the sum of the squares of the Miller indices is 54, in units of cps. Effect of the Invention

[0012] The Zn-Ni alloy plating layer of the metal pipe for oil well according to the present disclosure has high adhesion. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram showing the relationship between Fn1 (=I18 / (I18+I36+I54)) in this example and the adhesion evaluation, which is an index of adhesion. [Diagram 2] FIG. 2 is a configuration diagram showing an example of the metallic oil well pipe according to this embodiment. [Diagram 3] FIG. 3 is a partial cross-sectional view showing a cross section (longitudinal cross section) taken along the pipe axis direction of the coupling of the metal pipe for oil well shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view of a portion of the metallic pipe for oil well use shown in FIG. 3 in the vicinity of a pin, taken along a line parallel to the axial direction of the metallic pipe for oil well use. [Diagram 5] FIG. 5 is a cross-sectional view of a portion of the metallic pipe for oil well use shown in FIG. 3 in the vicinity of the box, taken along a line parallel to the axial direction of the metallic pipe for oil well use. [Figure 6] FIG. 6 is a partial cross-sectional view showing a cross section (longitudinal cross section) taken along the pipe axis direction of a coupling for a metal pipe for oil wells according to this embodiment, which is different from FIG. [Figure 7] FIG. 7 is a configuration diagram of the integral type metal oil well pipe according to this embodiment. [Figure 8] FIG. 8 is an enlarged view of the pin contact surface shown in FIG. [Figure 9] FIG. 9 is an enlarged view of the box contact surface shown in FIG. [Figure 10] FIG. 10 is an enlarged view of the pin contact surface having a different configuration from that of FIG. [Figure 11] FIG. 11 is an enlarged view of the box contact surface having a different configuration from that of FIG. [Figure 12] FIG. 12 is an enlarged view of the pin contact surface having a different configuration to that of FIGS. [Figure 13]FIG. 13 is an enlarged view of the box contact surface having a different configuration from that of FIGS. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, the present embodiment will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference characters and their description will not be repeated.

[0015] The present inventors have conducted detailed studies on a means for improving the adhesion of a Zn-Ni alloy plating layer formed on at least one of a pin contact surface and a box contact surface of a metal pipe for oil wells, and as a result, have obtained the following findings.

[0016] The physical and chemical properties of metal materials are affected by the crystallographic structure of the material and the microstructure represented by the surface morphology. Therefore, the present inventors have focused on the microstructure of the Zn-Ni alloy plating layer, which is a metal material, and have studied in detail means for improving the adhesion of the Zn-Ni alloy plating layer. As a result, the present inventors have found that the adhesion changes depending on the orientation of the crystals in the Zn-Ni alloy plating layer. In this specification, the distribution state of the orientation of the crystals in the Zn-Ni alloy plating layer is also referred to as the "orientation of the Zn-Ni alloy plating layer". In other words, the present inventors thought that if the orientation of the Zn-Ni alloy plating layer can be appropriately controlled, the adhesion of the Zn-Ni alloy plating layer could be improved.

[0017] One method for evaluating the orientation of metal materials is X-ray diffraction analysis (XRD). XRD analyzes the diffraction that occurs as a result of X-rays being scattered and interfered with by electrons around the atoms. As a result, XRD can obtain a unique diffraction pattern for each arrangement of atoms in a material. In other words, the size of the crystals and the orientation of the material can be evaluated from the diffraction patterns obtained by XRD.

[0018] Therefore, the present inventors manufactured various oil well metal pipes having a Zn-Ni alloy plating layer formed on the contact surface, evaluated the orientation of the Zn-Ni alloy plating layer by XRD, and investigated the relationship between the orientation and adhesion of the Zn-Ni alloy plating layer. As a result, it was found that the adhesion of the Zn-Ni alloy plating layer is significantly improved if the X-ray diffraction intensity of the Zn-Ni alloy plating layer satisfies the following formula (1). I 18 / (I 18 +I 36 +I 54 )≧0.60 (1) Here, I in formula (1) 18 The X-ray diffraction intensities of {411} and {330}, where the sum of the squares of the Miller indices is 18, are substituted in the unit of cps. 36 The X-ray diffraction intensities of {442} and {600}, which have a sum of squares of Miller indices of 36, are substituted in the unit of cps for I 54 is substituted with the X-ray diffraction intensity of {552}, where the sum of the squares of the Miller indices is 54, in units of cps.

[0019] Fn1=I 18 / (I 18 +I 36 +I 54 ) Fn1 is an index showing the orientation tendency of {411} and {330}. In other words, the larger Fn1 is, the more {411} and {330} are aligned in the same direction. As a result of further detailed studies by the present inventors, it has become clear that when Fn1 is 0.60 or more, the adhesion of the Zn-Ni alloy plating layer is significantly improved. This point will be specifically explained with reference to the drawings.

[0020] FIG. 1 shows the Fn1 (=I 18 / (I 18 +I 36 +I 541 is a diagram showing the relationship between the Fn1 and the adhesion evaluation, which is an index of adhesion. FIG. 1 was created using an embodiment described later. The X-ray diffraction intensity for determining Fn1 and the adhesion evaluation were determined by the method described later. The adhesion evaluation was given as "0" when there was the least amount of peeling, and as "5" when there was the most amount of peeling.

[0021] 1, when Fn1 is 0.60 or more, the adhesion evaluation is rapidly decreased. In other words, when Fn1 is 0.60 or more, the adhesion of the Zn-Ni alloy plating layer is significantly increased. Therefore, in the metal pipe for oil well according to the present embodiment, Fn1 is set to 0.60 or more in the Zn-Ni alloy plating layer formed on the contact surface.

[0022] The details of why the adhesion of the Zn-Ni alloy plating layer is improved when Fn1 is 0.60 or more are not clear. However, the present inventors speculate as follows. As described above, the physical and chemical properties of metal materials are affected by the crystallographic structure of the material. In other words, if the orientation of the Zn-Ni alloy plating layer is different, the ease with which distortion remains in the crystal lattice may also change. Here, if {411} and {330} are aligned in the same direction, there is a possibility that distortion is less likely to remain. As a result, the present inventors believe that if Fn1 is increased to 0.60 or more, the residual tensile stress in the Zn-Ni alloy plating layer can be reduced and adhesion can be improved.

[0023] The present inventors speculate that the adhesion of the Zn-Ni alloy plating layer with Fn1 of 0.60 or more is improved by the above mechanism. It is possible that the adhesion of the Zn-Ni alloy plating layer with Fn1 of 0.60 or more is improved by a mechanism different from the above mechanism. However, it is proved by the examples described later that the adhesion of the Zn-Ni alloy plating layer is improved by making Fn1 0.60 or more.

[0024] The essential features of the metal pipe for oil well according to the present embodiment, which has been completed based on the above findings, are as follows.

[0025] [1] A metal pipe for oil wells, comprising: a tube body including a first end and a second end; The tube body includes: A pin formed on the first end; a box formed at the second end; The pin is a pin contact surface including an external thread; The box includes: a box contact surface including an internal thread; The oil well metal pipe further comprises: a Zn-Ni alloy plating layer formed on at least one of the pin contact surface and the box contact surface; The X-ray diffraction intensity of the Zn-Ni alloy plating layer satisfies formula (1), Metal pipes for oil wells. I 18 / (I 18 +I 36 +I 54 )≧0.60 (1) Here, I in formula (1) 18 The X-ray diffraction intensities of {411} and {330}, where the sum of the squares of the Miller indices is 18, are substituted in the unit of cps. 36 The X-ray diffraction intensities of {442} and {600}, which have a sum of squares of Miller indices of 36, are substituted in the unit of cps for I 54 is substituted with the X-ray diffraction intensity of {552}, where the sum of the squares of the Miller indices is 54, in units of cps.

[0026] [2] The metal pipe for oil well use according to [1], The thickness of the Zn-Ni alloy plating layer is 5 to 25 μm. Metal pipes for oil wells.

[0027] [3] The metal pipe for oil well use according to [1] or [2], A lubricating coating is provided on or above the Zn-Ni alloy plating layer. Metal pipes for oil wells.

[0028] The metallic oil well pipe according to this embodiment will be described in detail below.

[0029] [Configuration of metal pipe for oil wells] First, the configuration of the metal pipe for oil well use according to the present embodiment will be described. The metal pipe for oil well use has a well-known configuration. There are T&C type metal pipe for oil well use and integral type metal pipe for oil well use. Each type of metal pipe for oil well use will be described in detail below.

[0030] [When the oil well metal pipe is T&C type] Fig. 2 is a configuration diagram showing an example of a metal pipe for oil well use 1 according to this embodiment. Fig. 2 is a configuration diagram of a so-called T&C (Threaded and Coupled) metal pipe for oil well use 1. Referring to Fig. 2, the metal pipe for oil well use 1 includes a pipe main body 10.

[0031] The pipe body 10 extends in the pipe axis direction. A cross section of the pipe body 10 perpendicular to the pipe axis direction is circular. The pipe body 10 includes a first end 10A and a second end 10B. The first end 10A is the end opposite to the second end 10B. In the T&C type metal pipe for oil wells 1 shown in FIG. 2, the pipe body 10 includes a pin pipe body 11 and a coupling 12. The coupling 12 is attached to one end of the pin pipe body 11. More specifically, the coupling 12 is fastened to one end of the pin pipe body 11 by a screw.

[0032] Fig. 3 is a partial cross-sectional view showing a cross section (longitudinal cross section) parallel to the pipe axis direction of the coupling 12 of the metal pipe for oil well use 1 shown in Fig. 2. With reference to Figs. 2 and 3, the pipe body 10 includes a pin 40 and a box 50. The pin 40 is formed at a first end portion 10A of the pipe body 10. When fastening, the pin 40 is inserted into a box 50 of another metal pipe for oil well use (not shown) and fastened to the box 50 of the other metal pipe for oil well use 1 by a screw.

[0033] The box 50 is formed at the second end 10B of the pipe body 10. During fastening, the pin 40 of another metal pipe for oil well use 1 is inserted into the box 50, and fastened to the pin 40 of the other metal pipe for oil well use 1 by a screw.

[0034] [Pin configuration] Fig. 4 is a cross-sectional view parallel to the pipe axis direction of the metal pipe for oil wells 1, showing a portion near the pin 40 of the metal pipe for oil wells 1 shown in Fig. 3. The dashed line portion in Fig. 4 shows the configuration of a box 50 of another metal pipe for oil wells 1 when fastening to another metal pipe for oil wells 1. Referring to Fig. 4, the pin 40 has a pin contact surface 400 on the outer circumferential surface of the first end 10A of the pipe body 10. The pin contact surface 400 comes into contact with the box 50 of the other metal pipe for oil wells 1 when fastening to the other metal pipe for oil wells 1.

[0035] The pin contact surface 400 includes at least the male thread portion 41 formed on the outer circumferential surface of the first end portion 10A. The pin contact surface 400 may further include a pin seal surface 42 and a pin shoulder surface 43. In FIG. 4, the pin seal surface 42 is disposed on the outer circumferential surface of the first end portion 10A, closer to the tip of the first end portion 10A than the male thread portion 41. That is, the pin seal surface 42 is disposed between the male thread portion 41 and the pin shoulder surface 43. The pin seal surface 42 is tapered. Specifically, the outer diameter of the pin seal surface 42 gradually decreases from the male thread portion 41 toward the pin shoulder surface 43 in the longitudinal direction (pipe axis direction) of the first end portion 10A.

[0036] When fastening with another metal pipe for oil wells 1, the pin seal surface 42 comes into contact with a box seal surface 52 (described later) of a box 50 of the other metal pipe for oil wells 1. More specifically, when fastening, the pin 40 is inserted into the box 50 of the other metal pipe for oil wells 1, so that the pin seal surface 42 comes into contact with the box seal surface 52. Then, when the pin 40 is further screwed into the box 50 of the other metal pipe for oil wells 1, the pin seal surface 42 comes into close contact with the box seal surface 52. As a result, when fastening, the pin seal surface 42 comes into close contact with the box seal surface 52 to form a seal based on metal-metal contact. Therefore, the airtightness of the metal pipes for oil wells 1 fastened to each other can be improved.

[0037] In FIG. 4, the pin shoulder surface 43 is disposed on the tip surface of the first end portion 10A. That is, in the pin 40 shown in FIG. 4, the male thread portion 41, the pin seal surface 42, and the pin shoulder surface 43 are disposed in this order from the center of the pipe body 10 toward the first end portion 10A. When fastening with another metal pipe for oil wells 1, the pin shoulder surface 43 faces and contacts a box shoulder surface 53 (described later) of a box 50 of the other metal pipe for oil wells 1. More specifically, when fastening, the pin 40 is inserted into the box 50 of the other metal pipe for oil wells 1, so that the pin shoulder surface 43 contacts the box shoulder surface 53. This allows a high torque to be obtained when fastening. Also, the positional relationship between the pin 40 and the box 50 in the fastened state can be stabilized.

[0038] It should be noted that the pin contact surface 400 of the pin 40 includes at least the male thread portion 41. In other words, the pin contact surface 400 may include the male thread portion 41, and not include the pin seal surface 42 and the pin shoulder surface 43. The pin contact surface 400 may include the male thread portion 41 and the pin shoulder surface 43, and not include the pin seal surface 42. The pin contact surface 400 may include the male thread portion 41 and the pin seal surface 42, and not include the pin shoulder surface 43.

[0039] [About the box configuration] Fig. 5 is a cross-sectional view parallel to the pipe axis direction of the metal pipe for oil wells 1, showing a portion near the box 50 of the metal pipe for oil wells 1 shown in Fig. 3. The dashed line portion in Fig. 5 shows the configuration of the pin 40 of the other metal pipe for oil wells 1 when fastening to the other metal pipe for oil wells 1. Referring to Fig. 5, the box 50 has a box contact surface 500 on the inner peripheral surface of the second end portion 10B of the pipe body 10. When fastening to the other metal pipe for oil wells 1, the pin 40 of the other metal pipe for oil wells 1 is screwed into the box contact surface 500, and the box contact surface 500 comes into contact with the pin contact surface 400 of the pin 40.

[0040] The box contact surface 500 includes at least a female thread portion 51 formed on the inner circumferential surface of the second end portion 10B. During fastening, the female thread portion 51 meshes with the male thread portion 41 of the pin 40 of another metal pipe for oil well 1.

[0041] The box contact surface 500 may further include a box seal surface 52 and a box shoulder surface 53. In FIG. 5, the box seal surface 52 is disposed on the inner circumferential surface of the second end portion 10B closer to the pipe body 10 than the female thread portion 51. That is, the box seal surface 52 is disposed between the female thread portion 51 and the box shoulder surface 53. The box seal surface 52 is tapered. Specifically, the inner diameter of the box seal surface 52 gradually decreases from the female thread portion 51 toward the box shoulder surface 53 in the longitudinal direction (pipe axis direction) of the second end portion 10B.

[0042] When fastening with another metal pipe for oil wells 1, the box seal surface 52 comes into contact with the pin seal surface 42 of the pin 40 of the other metal pipe for oil wells 1. More specifically, when fastening, the pin 40 of the other metal pipe for oil wells 1 is screwed into the box 50, so that the box seal surface 52 comes into contact with the pin seal surface 42, and when further screwed, the box seal surface 52 comes into close contact with the pin seal surface 42. As a result, when fastening, the box seal surface 52 comes into close contact with the pin seal surface 42 to form a seal based on metal-metal contact. Therefore, the airtightness of the metal pipes for oil wells 1 fastened to each other can be improved.

[0043] The box shoulder surface 53 is disposed closer to the pipe body 10 than the box seal surface 52. That is, in the box 50, the box shoulder surface 53, the box seal surface 52, and the female thread portion 51 are disposed in this order from the center of the pipe body 10 toward the tip of the second end 10B. When fastening with another metal pipe for oil wells 1, the box shoulder surface 53 faces and contacts the pin shoulder surface 43 of the pin 40 of the other metal pipe for oil wells 1. More specifically, when fastening, the pin 40 of the other metal pipe for oil wells 1 is inserted into the box 50, so that the box shoulder surface 53 contacts the pin shoulder surface 43. This allows a high torque to be obtained when fastening. Also, the positional relationship between the pin 40 and the box 50 in the fastened state can be stabilized.

[0044] The box contact surface 500 includes at least an internal thread portion 51. During fastening, the internal thread portion 51 of the box contact surface 500 of the box 50 corresponds to and contacts the external thread portion 41 of the pin contact surface 400 of the pin 40. The box seal surface 52 corresponds to and contacts the pin seal surface 42. The box shoulder surface 53 corresponds to and contacts the pin shoulder surface 43.

[0045] When the pin contact surface 400 includes the male threads 41 and does not include the pin seal surface 42 and the pin shoulder surface 43, the box contact surface 500 includes the female threads 51 and does not include the box seal surface 52 and the box shoulder surface 53. When the pin contact surface 400 includes the male threads 41 and the pin shoulder surface 43 and does not include the pin seal surface 42, the box contact surface 500 includes the female threads 51 and the box shoulder surface 53 and does not include the box seal surface 52. When the pin contact surface 400 includes the male threads 41 and the pin seal surface 42 and does not include the pin shoulder surface 43, the box contact surface 500 includes the female threads 51 and the box seal surface 52 and does not include the box shoulder surface 53.

[0046] The pin contact surface 400 may include a plurality of male threads 41, a plurality of pin seal surfaces 42, and a plurality of pin shoulder surfaces 43. For example, in the pin contact surface 400 of the pin 40, the pin shoulder surface 43, the pin seal surface 42, the male threads 41, the pin seal surface 42, the pin shoulder surface 43, the pin seal surface 42, and the male threads 41 may be arranged in this order from the tip of the first end 10A toward the center of the pipe body 10. In this case, in the box contact surface 500 of the box 50, the female threads 51, the box seal surface 52, the box shoulder surface 53, the box seal surface 52, the female threads 51, the box seal surface 52, and the box shoulder surface 53 are arranged in this order from the tip of the second end 10B toward the center of the pipe body 10.

[0047] 4 and 5 show a so-called premium joint in which the pin 40 includes the male thread portion 41, the pin seal surface 42, and the pin shoulder surface 43, and the box 50 includes the female thread portion 51, the box seal surface 52, and the box shoulder surface 53. However, as described above, the pin 40 may include the male thread portion 41 and not include the pin seal surface 42 and the pin shoulder surface 43. In this case, the box 50 includes the female thread portion 51 and does not include the box seal surface 52 and the box shoulder surface 53. FIG. 6 is a diagram showing an example of the metal pipe for oil well 1 in which the pin 40 includes the male thread portion 41 and does not include the pin seal surface and the pin shoulder surface, and the box 50 includes the female thread portion 51 and does not include the box seal surface and the box shoulder surface. The metal pipe for oil well 1 according to this embodiment may have the configuration shown in FIG. 6.

[0048] [When the oil well metal pipe is an integral type] The metal pipe for oil well use 1 shown in Figures 2, 3 and 6 is a so-called T&C type metal pipe for oil well use 1 in which a pipe body 10 includes a pin pipe body 11 and a coupling 12. However, the metal pipe for oil well use 1 according to the present embodiment may be an integral type instead of a T&C type.

[0049] FIG. 7 is a configuration diagram of an integral type metal pipe for oil wells 1 according to this embodiment. Referring to FIG. 7, the integral type metal pipe for oil wells 1 includes a pipe body 10. The pipe body 10 includes a first end 10A and a second end 10B. The first end 10A is disposed on the opposite side to the second end 10B. As described above, in the T&C type metal pipe for oil wells 1, the pipe body 10 includes a pin pipe body 11 and a coupling 12. That is, in the T&C type metal pipe for oil wells 1, the pipe body 10 is configured by fastening two separate members (the pin pipe body 11 and the coupling 12). In contrast, in the integral type metal pipe for oil wells 1, the pipe body 10 is integrally formed.

[0050] The pin 40 is formed at a first end 10A of the pipe body 10. When fastening, the pin 40 is inserted into and screwed into a box 50 of another integral type metal pipe for oil wells 1, and is fastened to the box 50 of the other integral type metal pipe for oil wells 1. The box 50 is formed at a second end 10B of the pipe body 10. When fastening, the pin 40 of the other integral type metal pipe for oil wells 1 is inserted into and screwed into the box 50, and is fastened to the pin 40 of the other integral type metal pipe for oil wells 1.

[0051] The configuration of the pin 40 of the integral type metal pipe for oil wells 1 is the same as that of the pin 40 of the T&C type metal pipe for oil wells 1 shown in FIG. 4. Similarly, the configuration of the box 50 of the integral type metal pipe for oil wells 1 is the same as that of the box 50 of the T&C type metal pipe for oil wells 1 shown in FIG. 5. In FIG. 7, the pin shoulder surface, the pin seal surface, and the male thread portion 41 are arranged in this order in the pin 40 from the tip of the first end 10A toward the center of the pipe body 10. Therefore, in the box 50, the female thread portion 51, the box seal surface, and the box shoulder surface are arranged in this order from the tip of the second end 10B toward the center of the pipe body 10. However, as in FIG. 4, the pin contact surface 400 of the pin 40 of the integral type metal pipe for oil wells 1 only needs to include at least the male thread portion 41. As in FIG. 5, the box contact surface 500 of the box 50 of the integral type metal pipe for oil wells 1 only needs to include at least the female thread portion 51.

[0052] In short, the metal oil well pipe 1 according to the present embodiment may be of either the T&C type or the integral type.

[0053] [Chemical composition of the tube body] In the metal oil well pipe 1 according to the present embodiment, the chemical composition of the pipe body 10 is not particularly limited. The pipe body 10 may have a chemical composition corresponding to carbon steel or a chemical composition corresponding to stainless steel.

[0054] [About the Zn-Ni alloy plating layer] In the metal oil well pipe 1 according to this embodiment, a Zn-Ni alloy plating layer is formed on at least one of the pin contact surface 400 and the box contact surface 500. That is, the Zn-Ni alloy plating layer is formed on the pin contact surface 400, but does not necessarily have to be formed on the box contact surface 500. Also, the Zn-Ni alloy plating layer is formed on the box contact surface 500, but does not necessarily have to be formed on the pin contact surface 400. Also, the Zn-Ni alloy plating layer may be formed on both the pin contact surface 400 and the box contact surface 500.

[0055] In the following description, the configuration on the pin contact surface 400 when a Zn-Ni alloy plating layer is formed on the pin contact surface 400, and the configuration on the box contact surface 500 when a Zn-Ni alloy plating layer is formed on the box contact surface 500 will be described.

[0056] [Configuration of the pin contact surface when a Zn-Ni alloy plating layer is formed on the pin contact surface] Fig. 8 is an enlarged view of the vicinity of the pin contact surface 400 when the Zn-Ni alloy plating layer 100 is formed on the pin contact surface 400. Referring to Fig. 8, in this case, the metal pipe for oil well 1 further includes the Zn-Ni alloy plating layer 100 formed on the pin contact surface 400 of the pin 40.

[0057] The Zn-Ni alloy plating layer 100 may be formed on a part of the pin contact surface 400, or may be formed on the entire pin contact surface 400. The pin seal surface 42 is subjected to particularly high surface pressure in the final stage of screw tightening. Therefore, when the Zn-Ni alloy plating layer 100 is formed partially on the pin contact surface 400, it is preferable that the Zn-Ni alloy plating layer 100 is formed at least on the pin seal surface 42. The Zn-Ni alloy plating layer 100 may be formed on the entire pin contact surface 400, as described above.

[0058] [Configuration of the box contact surface when a Zn-Ni alloy plating layer is formed on the box contact surface] FIG. 9 is an enlarged view of the vicinity of the box contact surface 500 when the Zn-Ni alloy plating layer 100 is formed on the box contact surface 500. Referring to FIG. 9, in this case, the Zn-Ni alloy plating layer 100 is formed on the box contact surface 500. The Zn-Ni alloy plating layer 100 may be formed on a part of the box contact surface 500, or may be formed on the entire box contact surface 500. The box seal surface 52 is subjected to a particularly high surface pressure in the final stage of screw tightening. Therefore, when the Zn-Ni alloy plating layer 100 is partially formed on the box contact surface 500, the Zn-Ni alloy plating layer 100 is preferably formed on at least the box seal surface 52.

[0059] [Composition of Zn-Ni alloy plating layer] As described above, the Zn-Ni alloy plating layer 100 is formed on at least one of the contact surfaces of the pin contact surface 400 and the box contact surface 500. Here, the Zn-Ni alloy plating layer 100 is made of a Zn-Ni alloy. Specifically, the Zn-Ni alloy contains zinc (Zn) and nickel (Ni). The Zn-Ni alloy may contain impurities. Here, the impurities of the Zn-Ni alloy refer to substances other than Zn and Ni that are contained in the Zn-Ni alloy plating layer 100 during the manufacture of the metal pipe for oil well 1, etc., and are contained in an amount that does not affect the effects of this embodiment.

[0060] Here, the Zn-Ni alloy plating layer 100 contains Zn. Zn is a less noble metal than Fe. Therefore, the Zn-Ni alloy plating layer 100 corrodes preferentially over the steel material (sacrificial corrosion protection). This enhances the corrosion resistance of the metal pipe for oil well 1.

[0061] The chemical composition of the Zn-Ni alloy plating layer 100 can be measured by the following method. A sample containing the Zn-Ni alloy plating layer 100 (including the contact surface on which the Zn-Ni alloy plating layer 100 is formed) is collected from the oil well metal pipe 1. The Zn-Ni alloy plating layer 100 of the collected sample is dissolved in hydrochloric acid with a concentration of 10% to obtain a solution. An elemental analysis is performed on the obtained solution by inductively coupled plasma atomic emission spectrometry (ICP-AES) to determine the Ni content (mass%) and Zn content (mass%) in the Zn-Ni alloy plating layer 100.

[0062] [Thickness of Zn-Ni alloy plating layer 100] The thickness of the Zn-Ni alloy plating layer 100 is not particularly limited. The thickness of the Zn-Ni alloy plating layer 100 is, for example, 1 to 20 μm. If the thickness of the Zn-Ni alloy plating layer 100 is 1 μm or more, the seizure resistance can be further improved. Even if the thickness of the Zn-Ni alloy plating layer 100 exceeds 20 μm, the above effect is saturated. The lower limit of the thickness of the Zn-Ni alloy plating layer 100 is preferably 3 μm, more preferably 5 μm. The upper limit of the thickness of the Zn-Ni alloy plating layer 100 is preferably 18 μm, more preferably 15 μm.

[0063] In this embodiment, the thickness of the Zn-Ni alloy plating layer 100 can be measured by the following method. The thickness of the Zn-Ni alloy plating layer 100 is measured at any four points on the pin contact surface 400 or the box contact surface 500 on which the Zn-Ni alloy plating layer 100 is formed, using an eddy current phase-type thickness gauge PHASCOPE PMP10 manufactured by Helmut Fischer GmbH. The measurement is performed by a method conforming to ISO (International Organization for Standardization) 21968 (2005). The measurement points are four points (four points at 0°, 90°, 180°, and 270°) in the circumferential direction of the metal pipe for oil well 1. The arithmetic mean value of the measurement results is taken as the thickness of the Zn-Ni alloy plating layer 100.

[0064] [Microstructure of Zn-Ni alloy plating layer 100] The Zn-Ni alloy plating layer 100 includes a γ phase. Here, the Zn-Ni alloy formed by electroplating includes an η phase, a γ phase, and an α phase. The η phase is a phase having a chemical formula of Zn and a hexagonal crystal structure. The γ phase is a phase having a chemical formula of Ni5Zn 21 and has a body-centered cubic crystal structure. The α phase is a phase whose chemical formula is Ni and has a face-centered cubic crystal structure. The Zn-Ni alloy plating layer 100 according to the present embodiment may be a mixed phase of the η phase, the γ phase, and the α phase. Preferably, the Zn-Ni alloy plating layer 100 is a single γ phase. In this specification, the term "single γ phase" means that the amount of phases other than the γ phase (i.e., the η phase and the α phase) is negligibly small.

[0065] [Orientation of Zn-Ni alloy plating layer 100] The Zn-Ni alloy plating layer 100 of this embodiment has an X-ray diffraction intensity that satisfies the following formula (1). I 18 / (I 18 +I 36 +I 54 )≧0.60 (1) Here, I in formula (1) 18The X-ray diffraction intensities of {411} and {330}, where the sum of the squares of the Miller indices is 18, are substituted in the unit of cps. 36 The X-ray diffraction intensities of {442} and {600}, which have a sum of squares of Miller indices of 36, are substituted in the unit of cps for I 54 is substituted with the X-ray diffraction intensity of {552}, where the sum of the squares of the Miller indices is 54, in units of cps.

[0066] Fn1(=I 18 / (I 18 +I 36 +I 54 )) is an index showing the orientation tendency of {411} and {330}. In other words, the larger Fn1 is, the more {411} and {330} are aligned in the same direction. In addition, when Fn1 is 0.60 or more, the adhesion of the Zn-Ni alloy plating layer 100 is significantly improved. Therefore, in this embodiment, Fn1 obtained from the X-ray diffraction intensity of the Zn-Ni alloy plating layer 100 is set to 0.60 or more.

[0067] The lower limit of Fn1 is preferably 0.65, more preferably 0.70, more preferably 0.75, more preferably 0.80, more preferably 0.85, and more preferably 0.90. The upper limit of Fn1 is not particularly limited. Fn1 may be 1.00. However, in the metal pipe for oil well 1 according to the present embodiment, the upper limit of Fn1 is substantially 0.99.

[0068] As described above, in this specification, the orientation of the Zn-Ni alloy plating layer 100 means the distribution state of the crystal orientation in the Zn-Ni alloy plating layer. Furthermore, the orientation of the material can be evaluated by XRD. However, there are cases where some planes cannot be separated by XRD. Specifically, the Miller indices of any plane are expressed as (hkl). In this case, there is not one diffraction line for each plane (hkl), but rather the sum of squares of the Miller indices s (=h 2 +k 2 +l 2In other words, diffraction lines originating from planes having the same value of the sum of squares of Miller indices s are obtained as one diffraction line.

[0069] Furthermore, the symmetrically related planes (411), (141), and (114) are collectively referred to as {411}. Similarly, the symmetrically related planes (330), (303), and (033) are collectively referred to as {330}. {411} and {330} are both s=18. Therefore, the diffraction line at s=18 is a superposition of the diffraction line originating from {411} and the diffraction line originating from {330}. Moreover, {442}, which is a collective term for the symmetrically related planes (442), (424), and (244), and {600}, which is a collective term for the symmetrically related planes (600), (060), and (006), are all s=36. Therefore, the diffraction line at s=36 is a superposition of the diffraction line originating from {442} and the diffraction line originating from {600}.

[0070] Thus, I in Eq. (1) 18 is the sum of the X-ray diffraction intensities of {411} and {330}. Similarly, I in formula (1) 36 is the sum of the X-ray diffraction intensities of {442} and {600}. 54 is the sum of the X-ray diffraction intensities of {552}, which collectively refers to the symmetrically related planes (552), (525), and (255).

[0071] In this embodiment, Fn1 can be obtained by the following method. A test piece is prepared from the pin contact surface 400 or the box contact surface 500 on which the Zn-Ni alloy plating layer 100 is formed of the metal pipe for oil well 1 according to this embodiment. The size of the test piece is not particularly limited, but is, for example, 15 mm x 15 mm x 2 mm thick. X-ray diffraction measurement is performed on the surface of the Zn-Ni alloy plating layer 100 of the test piece using an X-ray diffraction device. The X-ray diffraction measurement can be performed by a well-known method. The X-ray diffraction device is not particularly limited, and for example, RINT-2500 manufactured by Rigaku Corporation can be used. In this embodiment, the target of the X-ray diffraction device is not particularly limited. For example, Co (CoKα rays) may be used as the target of the X-ray diffraction device.

[0072] From the X-ray diffraction spectrum obtained by the X-ray diffraction measurement, the diffraction peaks corresponding to s = 18, 36, and 54 are identified. The intensities of the identified diffraction peaks are calculated, and I 18 , I 36 , and I 54 The obtained I 18 , I 36 , and I 54 From this, Fn1 can be calculated.

[0073] [Regarding other optional configurations of the metal pipe for oil well 1 of this embodiment] [About chemical conversion coating] The oil well metal pipe 1 of the present embodiment may further include a chemical conversion coating 110 on the Zn-Ni alloy plating layer 100. With reference to Fig. 10, in the case where the Zn-Ni alloy plating layer 100 is formed on the pin contact surface 400, the chemical conversion coating 110 may be formed on the Zn-Ni alloy plating layer 100. Also, with reference to Fig. 11, in the case where the Zn-Ni alloy plating layer 100 is formed on the box contact surface 500, the chemical conversion coating 110 may be formed on the Zn-Ni alloy plating layer 100.

[0074] The chemical conversion coating 110 is not particularly limited and may be a known chemical conversion coating. The chemical conversion coating 110 may be, for example, an oxalate chemical conversion coating, a phosphate chemical conversion coating, a borate chemical conversion coating, or a chromate coating. When the chemical conversion coating 110 is a chromate coating, it is preferable that the chromate coating does not contain hexavalent chromium.

[0075] The metal oil well pipe 1 may be stored outdoors for a long period of time before it is actually used in an oil well field. When the metal oil well pipe 1 is exposed to the atmosphere outdoors for a long period of time, the chemical conversion coating 110 can increase the corrosion resistance of the pin contact surface 400 and inhibit the occurrence of rust (white rust) on the pin contact surface 400. The film thickness of the chemical conversion coating 110 is not particularly limited. The film thickness of the chemical conversion coating 110 is, for example, 10 to 200 nm.

[0076] [Lubricating film] The metal pipe for oil well use 1 may further include a lubricating coating 120 on the Zn-Ni alloy plating layer 100, on the chemical conversion coating 110, or on a contact surface on which the Zn-Ni alloy plating layer 100 is not formed (on the pin contact surface 400 or on the box contact surface 500). The lubricating coating 120 further enhances the lubricity of the metal pipe for oil well use 1.

[0077] 12, in the case where the Zn-Ni alloy plating layer 100 is formed on the pin contact surface 400, the lubricating coating 120 may be formed on the chemical conversion coating 110 formed on the Zn-Ni alloy plating layer 100. That is, the lubricating coating 120 may be formed above the Zn-Ni alloy plating layer 100. Also, in the case where the Zn-Ni alloy plating layer 100 is formed on the box contact surface 500, the lubricating coating 120 may be formed on the Zn-Ni alloy plating layer 100. That is, the lubricating coating 120 may be formed on the Zn-Ni alloy plating layer 100.

[0078] The arrangement of the lubricating coating 120 is not limited to that shown in Fig. 12 and Fig. 13. In other words, the lubricating coating 120 may be formed on or above the pin contact surface 400 on which the Zn-Ni alloy plating layer 100 is not formed, may be formed on or above the box contact surface 500 on which the Zn-Ni alloy plating layer 100 is not formed, may be formed on or above the Zn-Ni alloy plating layer 100 formed on the pin contact surface 400, or may be formed on or above the Zn-Ni alloy plating layer 100 formed on the box contact surface 500.

[0079] The lubricating coating may be solid, semi-solid or liquid. A commercially available lubricant can be used for the lubricating coating. The lubricating coating contains, for example, lubricating particles and a binder. The lubricating coating may contain a solvent and other components as necessary. The lubricating particles are not particularly limited as long as they have lubricity. The lubricating particles are, for example, one or more selected from the group consisting of graphite, MoS2 (molybdenum disulfide), WS2 (tungsten disulfide), BN (boron nitride), PTFE (polytetrafluoroethylene), CFx (graphite fluoride) and CaCO3 (calcium carbonate).

[0080] The binder is, for example, one or two selected from the group consisting of organic binders and inorganic binders. The organic binder is, for example, one or two selected from the group consisting of thermosetting resins and thermoplastic resins. The thermosetting resin is, for example, one or more selected from the group consisting of polyethylene resins, polyimide resins, and polyamideimide resins. The inorganic binder is, for example, one or two selected from the group consisting of alkoxysilanes and compounds containing siloxane bonds. An example of a commercially available lubricant is SEAL-GUARD ECF (trade name) manufactured by JET-LUBE Co., Ltd. Another lubricating coating is, for example, a lubricating coating containing rosin, metal soap, wax, and lubricating powder.

[0081] [Method of manufacturing metal pipe for oil well 1] A method for producing the metal pipe for oil well use 1 of this embodiment will be described below. Note that, as long as the metal pipe for oil well use 1 of this embodiment has the above configuration, the method for producing it is not limited to the following method. However, the method for producing the metal pipe for oil well use 1 of this embodiment will be described below as a suitable example.

[0082] The method for manufacturing the metal pipe for oil well use 1 includes a preparation step (S1) of preparing a blank pipe on which the pins 40 or the boxes 50 are formed, and a Zn-Ni alloy plating layer forming step (S2). Each step of the method for manufacturing the metal pipe for oil well use 1 of the present embodiment will be described in detail below.

[0083] [Preparation process (S1)] In the preparation step (S1), a mother pipe on which a pin 40 or a box 50 is formed is prepared. In this specification, the term "mother pipe on which a pin or a box is formed" means any one of the pipe body 10 and the pin pipe body 11 of the T&C type metal pipe for oil well 1, and the pipe body 10 of the integral type metal pipe for oil well 1.

[0084] The mother pipe on which the pin 40 or the box 50 is formed is manufactured, for example, by the following method. A material is manufactured using molten steel. Specifically, a cast piece (slab, bloom, or billet) is manufactured using the molten steel by a continuous casting method. An ingot may be manufactured using the molten steel by an ingot casting method. If necessary, a steel piece (billet) may be manufactured by blooming the slab, bloom, or ingot. A material (slab, bloom, or billet) is manufactured by the above-mentioned steps. A mother pipe is manufactured by hot working the prepared material. The hot working method may be piercing rolling by the Mannesmann method or hot extrusion. The mother pipe after the hot working is subjected to a well-known quenching and a well-known tempering to adjust the strength of the mother pipe. A mother pipe is manufactured by the above-mentioned steps. When the oil well metal pipe 1 is a T&C type, a mother pipe for the coupling 12 is also prepared. The manufacturing method of the mother pipe for the coupling 12 is the same as the manufacturing method of the mother pipe described above.

[0085] When the metal pipe for oil well use 1 is of the T&C type, thread cutting is performed on the outer surfaces of both ends of a mother pipe for the pin pipe body 11 to form pins 40 including pin contact surfaces 400. Through the above steps, a mother pipe (pin pipe body 11) on which pins 40 are formed is prepared when the metal pipe for oil well use 1 is of the T&C type. When the metal pipe for oil well use 1 is of the T&C type, a coupling 12 may also be prepared. Specifically, thread cutting is performed on the inner surfaces of both ends of a mother pipe for the coupling 12 to form a box 50 including a box contact surface 500. Through the above steps, the coupling 12 is manufactured.

[0086] When the metal oil well pipe 1 is of an integral type, threading is performed on the outer surface of the first end 10A of the mother pipe to form a pin 40 including a pin contact surface 400. Furthermore, threading is performed on the inner surface of the second end 10B of the mother pipe to form a box 50 including a box contact surface 500. Through the above steps, a mother pipe (pipe body 10) on which the pin 40 and box 50 are formed is prepared when the metal oil well pipe 1 is of an integral type.

[0087] [Other optional processes] The preparation step (S1) of this embodiment may further include at least one of a grinding step and a Ni strike plating step.

[0088] When the grinding process is performed in the preparation process (S1) according to this embodiment, the grinding process includes, for example, sandblasting and mechanical grinding. Sandblasting is a process in which a blasting material (abrasive) is mixed with compressed air and projected onto the contact surface. The blasting material is, for example, spherical shot material and angular grid material. Sandblasting can increase the surface roughness of the contact surface. Sandblasting can be performed by a well-known method. For example, air is compressed with a compressor, and the compressed air is mixed with the blasting material. The material of the blasting material is, for example, stainless steel, aluminum, ceramic, alumina, etc. The conditions of the sandblasting process, such as the projection speed, are not particularly limited, and can be appropriately adjusted under well-known conditions.

[0089] In the Ni strike plating step, a Ni strike plating layer is formed on the surface of the mother tube. The Ni strike plating layer is a very thin undercoat plating layer that enhances the adhesion of the Zn-Ni alloy plating layer 100 described below. The plating bath used in the Ni strike plating step is not particularly limited, and any well-known bath can be used. The conditions for forming the Ni strike plating layer are also not particularly limited, and can be appropriately adjusted.

[0090] When the Ni strike plating step is performed, a Ni strike plating layer is formed between the pipe body 10 and the Zn-Ni alloy plating layer 100. On the other hand, the thickness of the Ni strike plating layer formed is negligibly thin compared to the thickness of the Zn-Ni alloy plating layer 100. That is, in the metal pipe for oil well 1 according to the present embodiment, the Zn-Ni alloy plating layer 100 may contain a Ni strike plating layer.

[0091] [Zn-Ni alloy plating layer formation process (S2)] In the Zn-Ni alloy plating layer formation step (S2), a Zn-Ni alloy plating layer 100 is formed by electroplating on the pin contact surface 400 of the bare tube on which the pin 40 is formed after the preparation step (S1) and / or on the box contact surface 500 of the bare tube on which the box 50 is formed.

[0092] In the Zn-Ni alloy plating layer forming step (S2), a plating bath containing zinc ions and nickel ions is used to form the Zn-Ni alloy plating layer 100. The counter anions of the zinc ions and nickel ions are not particularly limited. For example, a chloride ion or a sulfate ion may be used as the counter anion. That is, in the Zn-Ni alloy plating layer forming step (S2) according to the present embodiment, a chloride bath or a sulfate bath may be used as the plating bath.

[0093] Hereinafter, a specific example of a plating bath will be described in which a chloride bath is used. When a chloride bath is used, it is preferable that the plating bath does not contain a brightener. In this case, it is further preferable that the metal ion concentration in the plating bath is high. That is, when a chloride bath is used, specifically, it is preferable that the sum of the zinc ion concentration and the nickel ion concentration is 30 g / L or more, and the zinc ion concentration (g / L) is higher than the nickel ion concentration (g / L), and that the plating bath does not contain a brightener. In this case, Fn1 can be stably made 0.60 or more in the formed Zn-Ni alloy plating layer 100.

[0094] More specifically, in the Zn-Ni alloy plating layer forming step (S2) according to the present embodiment, for example, a plating bath containing 40 g / L of zinc ions, 30 g / L of nickel ions, and 240 g / L of ammonium chloride, and not containing a brightener, can be used. As described above, in the Zn-Ni alloy plating layer forming step (S2) according to the present embodiment, the plating bath is not limited to a chloride bath, and a sulfate bath or other plating baths can also be used.

[0095] The electroplating conditions in the Zn-Ni alloy plating layer forming step (S2) are not particularly limited and can be appropriately adjusted under well-known conditions. The electroplating conditions are, for example, plating bath pH: 1 to 10, plating bath temperature: 10 to 60° C., current density: 1 to 100 A / dm 2 and treatment time: 0.1 to 30 minutes. When the Zn-Ni alloy plating layer 100 is formed on the pin contact surface 400, the pin contact surface 400 is immersed in the above-mentioned plating bath to perform electroplating. On the other hand, when the Zn-Ni alloy plating layer 100 is formed on the box contact surface 500, the box contact surface 500 is immersed in the above-mentioned plating bath to perform electroplating.

[0096] The above-mentioned manufacturing process produces the metal pipe for oil well use 1 of the present embodiment having the above-mentioned configuration. Note that the above-mentioned manufacturing process is an example of a manufacturing process of the metal pipe for oil well use 1 of the present embodiment, and the manufacturing method of the metal pipe for oil well use 1 of the present embodiment is not limited to the above-mentioned manufacturing process.

[0097] [Other optional processes] The method for producing the metal oil well pipe 1 according to the present embodiment may further include at least one of the following chemical conversion treatment step and film formation step. These steps are optional. Therefore, these steps do not necessarily have to be performed.

[0098] [Chemical conversion treatment process] In the manufacturing method of this embodiment, a chemical conversion treatment step may be performed as necessary. That is, the chemical conversion treatment step is an optional step. When the chemical conversion treatment step is performed, a chemical conversion coating 110 is formed on the Zn-Ni alloy plating layer 100. In the chemical conversion treatment step, a well-known chemical conversion treatment may be performed. The chemical conversion treatment may be, for example, an oxalate chemical conversion treatment, a phosphate chemical conversion treatment, or a borate chemical conversion treatment. For example, when a phosphate chemical conversion treatment is performed, a chemical conversion treatment using zinc phosphate may be performed, a chemical conversion treatment using manganese phosphate may be performed, or a chemical conversion treatment using zinc calcium phosphate may be performed.

[0099] Specifically, when performing zinc phosphate conversion treatment, a conversion treatment solution containing, for example, 1 to 150 g / L of phosphate ions, 3 to 70 g / L of zinc ions, 1 to 100 g / L of nitrate ions, and 0 to 30 g / L of nickel ions can be used as the treatment solution. In this case, the liquid temperature of the conversion treatment solution is, for example, 20 to 100° C. In this way, the conversion treatment is performed by appropriately setting well-known conditions, whereby the chemical conversion coating 110 can be formed.

[0100] [Film forming process] In the manufacturing method of this embodiment, a film-forming step may be performed as necessary. That is, the film-forming step is an optional step. In the film-forming step, a lubricating coating is formed on the Zn-Ni alloy plating layer 100 and / or on the chemical conversion coating 110 and / or on the contact surface (the pin contact surface 400 or the box contact surface 500) on which the Zn-Ni alloy plating layer 100 is not formed.

[0101] In the film-forming step, a composition or lubricant containing the components of the lubricating coating described above is applied. This allows the lubricating coating to be formed. The application method is not particularly limited. Examples of application methods include spray application, brush application, and immersion. When spray application is employed, the composition or lubricant may be heated and sprayed in a state of enhanced fluidity. The composition or lubricant is dried to form the lubricating coating.

[0102] The metal pipe for oil well use 1 of this embodiment will be described in more detail below with reference to examples. The conditions in the following examples are one example of conditions adopted to confirm the feasibility and effects of the metal pipe for oil well use 1 of this embodiment. Therefore, the metal pipe for oil well use 1 of this embodiment is not limited to this one example of conditions. EXAMPLES

[0103] In this example, a Zn-Ni alloy plating layer was formed on a steel sheet simulating a contact surface, and the adhesion of the Zn-Ni alloy plating layer was evaluated. Specifically, the steel sheet was a cold-rolled steel sheet with a chemical composition of C≦0.15%, Mn≦0.60%, P≦0.100%, S≦0.050%, and the balance: Fe and impurities.

[0104] For the steel sheets with each test number, electrolytic degreasing, pickling with hydrochloric acid, and Ni strike plating were performed as surface preparation. The treatment time for Ni strike plating is shown in the "Surface preparation (min)" column in Table 1. Note that "-" in the "Surface preparation (min)" column in Table 1 means that Ni strike plating was not performed.

[0105] [Table 1]

[0106] A Zn-Ni alloy plating layer was formed on the steel sheet of each test number using the plating baths shown in Table 1. In addition, the thickness of the Zn-Ni alloy plating layer was about 10 μm in each case of using any plating bath. Furthermore, the Ni ratio in the Zn-Ni alloy plating layer was 12 to 16 mass %. Specifically, the plating baths "A" and "B" were as follows.

[0107] [Plating bath A] The plating bath A used was a product named Dynejin Alloy N2-PL manufactured by Yamato Kasei Kenkyusho Co., Ltd. The plating bath A was a chloride bath and did not contain a brightener. Furthermore, the sum of the zinc ion concentration and the nickel ion concentration of the plating bath A was 30 g / L or more, and the zinc ion concentration (g / L) was higher than the nickel ion concentration (g / L). The electroplating conditions when plating bath A was used were plating bath pH: 5.8, plating bath temperature: 40°C, current density: 6 A / dm 2 , and processing time: 8 minutes.

[0108] [Plating bath B] As plating bath B, a product named Dyndine Alloy N-PL manufactured by Yamato Kasei Kenkyusho Co., Ltd. was used. Plating bath B was a chloride bath and contained a brightener. Furthermore, the sum of the zinc ion concentration and nickel ion concentration in plating bath B was 30 g / L or more, but the zinc ion concentration (g / L) was lower than the nickel ion concentration (g / L). The electroplating conditions when plating bath B was used were plating bath pH: 6.4, plating bath temperature: 25°C, current density: 2 A / dm 2 , and processing time: 20 minutes.

[0109] For the steel sheets having each test number on which the Zn-Ni alloy plating layer was formed as described above, an X-ray diffraction intensity measurement test by XRD and an adhesion test were carried out.

[0110] [X-ray diffraction intensity measurement test] The X-ray diffraction intensity measurement test was carried out for the steel sheets of each test number by the above-mentioned method, and Fn1 was obtained. Specifically, X-ray diffraction measurement was carried out for the steel sheets of each test number using an X-ray diffraction device. The X-ray diffraction device used was a RINT-2500 manufactured by Rigaku Corporation. In addition, the target in the X-ray diffraction measurement was Co (CoKα radiation). From the X-ray diffraction spectrum obtained by the X-ray diffraction measurement, diffraction peaks corresponding to s = 18, 36, and 54 were identified. The intensities of the identified diffraction peaks were calculated, and I 18 , I 36, and I 54 The obtained I 18 , I 36 , and I 54 For each test number, the obtained I 18 , I 36 , I 54 , and Fn1 are shown in Table 1.

[0111] [Adhesion test] An adhesion test was carried out on the steel sheets of each test number according to the cross-cut method specified in JIS K 5600-5-6 (1999). Specifically, cuts were made with a cutter blade in a direction perpendicular to the Zn-Ni alloy plating layer of the steel sheets of each test number. Six parallel cuts were made at intervals of about 1 mm, and then the direction was changed by 90°, and six cuts perpendicular to the six cuts were made at intervals of about 1 mm. A transparent adhesive tape was applied to the area where the cuts were made, and the adhesive tape was removed within 5 minutes. The surface of the steel sheets of each test number after the adhesive tape was removed was visually observed, and the test results were classified into six levels from 0 to 5 according to the criteria of JIS K 5600-5-6 (1999). The classification with the least peeling was "0", and the classification with the most peeling was "5". The obtained test results are shown in the "Adhesion Evaluation" column of Table 1.

[0112] [Evaluation Results] Referring to Table 1, in the steel sheets of test numbers 1 to 6, the X-ray diffraction intensity of the Zn-Ni alloy plating layer satisfied formula (1). As a result, the adhesion evaluation in the adhesion test was 0 to 2. That is, the Zn-Ni alloy plating layers of test numbers 1 to 6 had high adhesion.

[0113] On the other hand, in the steel sheets of test numbers 7 to 9, the X-ray diffraction intensity of the Zn-Ni alloy plating layer did not satisfy formula (1). As a result, the adhesion evaluation in the adhesion test was 4 or 5. In other words, the Zn-Ni alloy plating layers of test numbers 7 to 9 did not have high adhesion.

[0114] The embodiments of the present disclosure have been described above. However, the above-described embodiments are merely examples for implementing the present disclosure. Therefore, the present disclosure is not limited to the above-described embodiments, and can be implemented by appropriately modifying the above-described embodiments without departing from the spirit of the present disclosure. [Explanation of symbols]

[0115] 1 Metal pipe for oil well 10 Tube body 10A 1st end 10B 2nd end 40 pin 41 Male thread 50 Box 51 Female thread 100 Zn-Ni alloy plating layer 110 Chemical conversion coating 120 Lubricating film 400 pin contact surface 500 Box Contact Surface

Claims

1. A metal pipe for oil wells, comprising: a tube body including a first end and a second end; The tube body includes: a pin formed on the first end; a box formed at the second end; The pin is a pin contact surface including an external thread; The box includes: a box contact surface including an internal thread; The oil well metal pipe further comprises: a Zn-Ni alloy plating layer formed on at least one of the pin contact surface and the box contact surface; The X-ray diffraction intensity of the Zn—Ni alloy plating layer satisfies formula (1). Metal pipes for oil wells. I 18 / (I 18 +I 36 +I 54 )≧0.60 (1) Here, I in formula (1) 18 The X-ray diffraction intensities of {411} and {330}, which give a sum of squares of Miller indices of 18, are substituted in the unit of cps for I 36 The X-ray diffraction intensities of {442} and {600}, which give a sum of squares of Miller indices of 36, are substituted in the unit of cps for I 54 The X-ray diffraction intensity of {552}, where the sum of the squares of the Miller indices is 54, is substituted in the unit of cps.

2. The metal pipe for oil well according to claim 1, The thickness of the Zn-Ni alloy plating layer is 5 to 25 μm. Metal pipes for oil wells.

3. The metal pipe for oil well according to claim 1 or 2, A lubricating coating is provided on or above the Zn-Ni alloy plating layer. Metal pipes for oil wells.

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